23 

 APPLE APHIDES.* 



The so-called " Aphis " or ' Blue Bug " Blight, which 

 attacks apples, and to a minor extent pears, is in some years 

 one of the worst pests fruit growers and gardeners have to 

 contend with in this country. The terms Aphis, Dolphin 

 or Blue Bug " Blight " are common names in all fruit-grow- 

 ing districts. They apply to damage done by several species 

 of plant lice or aphides. 



Of the eight species of aphides recorded as attacking the 

 apple in Great Britain only four are of general importance. 

 These are: (i) the Blue Bug or Eosy Apple Aphis (Aphis 

 malifolia, Fitch); (ii) the Green Apple Aphis (Aphis pomi, 

 De Geer); (iii) the Oat Apple Aphis (Siphocoryne avena 

 Fabr.), and the Woolly Aphis or American Blight (Schizoneura 

 lanigera, Hausmann). 



This leaflet deals only with the first three, which are 

 leaf, blossom, shoot or fruit feeders. In this respect they 

 are unlike the Woolly Aphis, which usually feeds on the 

 wood and roots, although in very bad attacks it may spread 

 to the leaves and fruit. This latter insect is dealt with in 

 Leaflet No. 34. By far the greatest amount of harm is done 

 by the Eosy Apple Aphis (Aphis maltfolia). but in some years 

 and in certain localities the Green Apple Aphis (Aphis pomi) 

 and the Oat Apple Aphis (Siphocoryne avena) are of 

 considerable importance. 



Nature of Damage. The damage by the- three species 

 of apple pests mentioned above is mainly to the foliage and 

 young wood, but also to some extent to the fruit, which is 

 stunted and deformed. The Oat Apple Aphis (Siphocoryne 

 avence) may damage the blossom as well as the leaves, and 

 in some seasons similar damage is done by the Blue Bug or 

 Eosy Apple Aphis (A. malifolice). The Green Apple Aphis 

 (A. pomi) mainly attacks the young shoots, and so densely 

 do the insects cluster on them that they check the growth. 

 They do not, however, produce such distortion as is caused 

 by A. malijolia. 



The Blue Bug or Eosy Apple Aphis (A. malifolia) causes 

 the leaves to curl up, and beneath this shelter the lice repro- 

 duce, in certain seasons, at a great rate. The foliage becomes 

 smothered and poisoned by their honey-dew and other 

 secretions and turns brown. In some cases they produce, 

 earlier in the year, yellow or rosy-red, galled masses on the 

 leaves. Later they may swarm on the leaf -stalks, shoots and 

 fruitlets, and by their punctures deform them. The leaves 

 may fall and only a few stunted and galled apples remain. 



* ATI abridged edition of an article, by Mr. F. V. Theobald, published 

 in the Journal of the Board of Agriculture, for April, 1919, pp. 63-71. 



